if they were to tour again this summer, which i highly doubt, but let's just assume they want to add one more stadiumleg.
where have they not brought their stadium show thus far... north america, africa, the middle east, india & southeast asia.
as much as bono is in love with africa, i don't see it. there aren't enough locations, other than perhaps south afria, where they could realisticly sell out a stadium. the mid-east and south-east asia is a tad volitile, so a show in, say, tel aviv again isn't exactly realistic, either. not in the current political climate. so where does that leave them to take the stadium gig? north america.
this rumor pretains to stadium gigs. if it were rumored arena shows, i would think europe would make the most sense because it's the biggest market yet to see the arena show. america is the biggest market yet to see the stadium show. thus it makes the most sense.